Thank you very much. This helped me to improve the function:
import os
_lf = b"\n"
_err_n = "Parameter n must be a positive integer number"
_err_chunk_size = "Parameter chunk_size must be a positive integer number"
def tail(filepath, n=10, chunk_size=100):
if (n <= 0):
raise ValueError(_err_n)
if (n % 1 != 0):
raise ValueError(_err_n)
if (chunk_size <= 0):
raise ValueError(_err_chunk_size)
if (chunk_size % 1 != 0):
raise ValueError(_err_chunk_size)
n_chunk_size = n * chunk_size
pos = os.stat(filepath).st_size
chunk_line_pos = -1
newlines_to_find = n
first_step = True
with open(filepath, "rb") as f:
text = bytearray()
while pos != 0:
pos -= n_chunk_size
if pos < 0:
pos = 0
f.seek(pos)
chars = f.read(n_chunk_size)
text[0:0] = chars
search_pos = n_chunk_size
while search_pos != -1:
chunk_line_pos = chars.rfind(_lf, 0, search_pos)
if first_step and chunk_line_pos == search_pos - 1:
newlines_to_find += 1
first_step = False
if chunk_line_pos != -1:
newlines_to_find -= 1
if newlines_to_find == 0:
break
search_pos = chunk_line_pos
if newlines_to_find == 0:
break
return bytes(text[chunk_line_pos+1:])
On Thu, 12 May 2022 at 20:29, Stefan Ram <r...@zedat.fu-berlin.de> wrote:
> I am not aware of a definition of "line" above,
> but the PLR says:
>
> |A physical line is a sequence of characters terminated
> |by an end-of-line sequence.
>
> . So 10 lines should have 10 end-of-line sequences.
>
Maybe. Maybe not. What if the file ends with no newline?
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